So far, as this kind of technology of the key arrangement for a portable terminal device, a portable terminal device described in Japanese Patent Application Laid-Open No. 2008-84144 is known.
In the portable terminal device described in Japanese Patent Application Laid-Open No. 2008-84144, a display part detects a continuously moving input using a touch panel that starts from one point in a display area of an operation key group displayed on the display part. After the detection, the one point corresponding to the starting point is designated as a fixed point, the starting point is moved according to the continuously moving input, and also, the display area of the operation key group is enlarged or reduced according to the movement of the starting point.
At the same time, a layout of the operation key group is changed by enlarging or reducing at least a part of the operation key group.
[PATENT DOCUMENT 1] Japanese Patent Application Laid-Open No. 2008-84144.